Electronic Supplementary Information

Electronic Supplementary Material (ESI) for Energy & Environmental Science. This journal is The Royal Society of Chemistry 0 Electronic Supplementary Information Slow surface passivation and crystal relaxation with additives to improve device performance and durability for tin-based perovskite solar cells Efat Jokar, 1 Cheng-Hsun Chien, 1 Amir Fathi, 1 Mohammad Rameez, 1 Chang-Yu Hao 1 and Eric Wei- Guang Diau 1, * 1 Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 01 Ta-Hsueh Rd., Hsinchu 300, Taiwan. Center for Emergent Functional Matter Science, National Chiao Tung University, 01 Ta-Hsueh Rd., Hsinchu 300, Taiwan; E-mail: diau@mail.nctu.edu.tw Experimental section Materials Butylammonium Iodide (BAI): BAI was prepared through the reaction of butylamine and HI (57% in water) at molar ratio 1:1 in an ice bath. The obtained powder was washed with diethyl ether several times and dried in a vacuum oven overnight at 50 C. Ethylenediammonium Diiodide (EDAI ): Ethylenediamine and HI were reacted in an ice bath at molar ratio (:5). Excess HI was added to ensure complete reaction. A white powder precipitated in the flask; a powder was separated and washed with diethyl ether several times. The obtained powder was dried in a vacuum oven overnight at 50 C. Device Fabrication Cleaned glasses coated with indium tin oxide (ITO) were treated with an oxygen plasma for 0 min. A PEDOT:PSS layer was then spin-coated onto these substrates at 5000 rpm for 60 s and dried at 150 C for min. The films were transferred into a glovebox for the deposition of a perovskite layer (O ppm, H O 0.5 ppm). The reference FASnI 3 film was spin-coated from a precursor solution (FAI 1 M, SnI 1M, SnF 0.1 M, in DMSO) at 5000 rpm for 90 s ( µl of PSK solution on cm cm substrate). 1

Chlorobenzene (800 μl) was dropped after 60 s during the spin-coating. After spin coating the dark red film that represented the formation of the FASnI 3 -DMSO complex was annealed at 0 C for min. Deposition of PSK film was done under flow of nitrogen in glovebox to avoid the accumulation of solvent inside of spin-coater. The perovskite structure was modified on adding BAI or EDAI. FASnI 3 - xbai films were prepared under the same conditions as the standard; x is the molar fraction of BAI and EDAI that was added to the perovskite solutions. The perovskite solutions contained BAI (x = 0.1, 0.15, 0. and 0.5 M), FAI ((1 x) M), SnI (1 M) and SnF (0.1 M). For FASnI 3 -yedai films, the solutions contained EDAI (y = 0.01, 0.0 and 0.03 M), FAI ((1 y) M), SnI (1 M) and SnF (0.1 M). Afterwards, electron-transfer and hole-blocking layers were coated via thermal evaporation (pressure 5-6 Torr); C 60 0 nm, BCP 6 nm were deposited. The silver back-contact electrode (0 nm) was eventually deposited via thermal evaporation. Characterization of materials and devices A field-emission scanning electron microscope (FESEM, Hitachi SU80) was used to investigate the morphology of the samples. The X-ray diffraction (XRD) patterns of the thin films coated on the ITO substrates were acquired with an X-ray diffractometer. The current density-voltage characteristics of devices were recorded with a digital source meter (Keithley 400) under one-sun illumination (AM 1.5G, 0 mw cm - ) from a solar simulator (XES-40S1, SAN-E1) and were calibrated with a silicon diode and a KG-5 filter to decrease the mismatch of the spectrum. All measurements were done under ambient conditions. The inciden-photon-to- current (IPCE) spectra were recorded with a system comprising a Xe lamp (A-, PTi, 150 W) and a monochromator (PTi). The absorption spectra of the thin-film and solution samples were recorded with a spectrophotometer (JASCO V-570). The PL transients were recorded with a time-correlated single-photon-counting (TCSPC) system (Fluotime 00, PicoQuant) with excitation at 635 nm from a picosecond pulsed-diode laser (LDH-635, PicoQuant, FWHM ~70 ps). The repetition rate of the laser used for all experiments was 5 MHz; the pulse energy was 4 μj cm -. The PL temporal profiles were collected at 850±3 nm, which covers the emission maximum but is at the edge of the sensitive region of the used MCP-PMT (R3809U-50), for all perovskite samples under investigation. X-ray photoelectron spectra (XPS) were recorded (Thermo K-ALPHA Surface Analysis) for perovskite films coated on ITO substrates. The samples were etched with a beam of ions (1 kev Ar + ) for 0 s and 30 s. Given a possible drift of the spectra, the curves were corrected based on the C1s line at 84.6eV.The electrochemical impedance spectra (EIS) of all devices were measured with an

electrochemical workstation (IM 6, Zahner, Germany) over frequency range 0 mhz - 4 MHz with ac amplitude mv under darkness at 0.3 V. The obtained EIS data were fitted (Z-view software) based on an equivalent- circuit model. Capacitance-voltage (C-V) measurements were conducted on applying a perturbation mv of AC voltage at frequency 1 khz, which was superimposed on the DC bias to yield the final C-V curves. The depletion capacitance C normalized to the area is given by C = (V fb V) qεε 0 n in which V is the applied voltage, q corresponds to the elementary charge, ε is the relative permittivity of the FASnI 3, ε 0 denotes the permittivity of vacuum, n is the total concentration of acceptor impurities and V fb is the flat-band potential of the contact. The abscissa intercept of the linear regime in a Mott Schottky plot provided the built-in potential. The flat-band potential, V fb of a PSC is generally defined as the compensating energetic potential difference required between the quasi-fermi level of perovskite (E P ) and that of ETL/cathode electron-selective contact (E Fn ) and is expressed mathematically as V fb = E Fn E P As other parameters were identical for all fabricated PSC, any variation in flat-band potential could be attributed to the variation in the quasi-fermi level of perovskite. 3

(a) (b) (c) (d) Figure S1. SEM images of FASnI 3 with varied proportions of BAI additive: (a) %, (b) 15 %, (c) 0 % and (d) 5 % 4

Figure S. SEM images of FASnI 3 with varied proportions of EDAI additive: (a) 0%, (b) 0.5 %, (c) 1 %, (d) %, (e) 3 % and (f) 5 % 5

(a) (b) (c) Figure S3. AFM images of (a) FASnI 3, (b) FASnI 3 -BAI 15 % and (c) FASnI 3 -EDAI 1%. AFM was measured in air (RH = 50%) and oxidation of the films may occur to produce the white spots as shown in (a) and (b). 6

(a) 1.8 Absorbance 1.6 1.4 1. 1.0 0.8 0.6 0.4 0. 0.0 400 500 600 700 800 900 Wavelength /nm FASnI 3 FASnI 3 -% BAI FASnI 3-15% BAI FASnI 3-0% BAI Absorbance (b).0 1.5 1.0 0.5 0.0 FASnI 3 FASnI 3-1% EDAI FASnI 3 - % EDAI FASnI 3-3% EDAI 400 500 600 700 800 900 Wavelength /nm Figure S4. UV-vis absorption spectra of thin-film samples of (a) FASnI 3 -xbai and (b) FASnI 3 -yedai with varied proportions of x and y. 7

Figure S5. Side-view SEM images of typical devices made of (a) FASnI 3 -BAI 15 % and (b) FASnI 3 - EDAI 1 % samples 8

0 (a) Current Density /ma cm - 14 1 8 6 4 FASnI 3 FASnI3-% BAI FASnI3-15% BAI FASnI3-0% BAI FASnI3-5% BAI 0 0.0 0.1 0. 0.3 0.4 0.5 Voltage /V (b) 80 IPCE /% 70 60 50 40 30 0 0 FASnI 3 BAI % BAI 15% BAI 0% BAI 5%.87(mA cm^-) 14.81 (ma cm^-).5(ma cm^-) 13.96 (ma cm^-) 13.40 (ma cm^-) 0 400 500 600 700 800 900 00 Wavelength /nm 14 1 8 6 4 Intergated current Density /ma cm - Figure S6. (a) Current-voltage and (b) corresponding IPCE spectra with integrated current densities of the devices made of FASnI 3 -xbai samples 9

Voc /V 0.5 0.50 0.48 0.46 0.44 0.4 0.40 0.38 0.36 0.34 0.3 0.30 FASnI3 BAI % BAI 15% BAI 0% Jsc /ma cm - 0 19 17 15 14 13 1 11 9 8 FASnI3 BAI % BAI 15% BAI 0% 6.0 0.70 5.5 FF 0.65 0.60 PCE /% 5.0 4.5 4.0 3.5 0.55 FASnI3 BAI % BAI 15% BAI 0% 3.0 FASnI3 BAI % BAI 15% BAI 0% Figure S7. Statistical boxplots of photovoltaic parameters for PSC devices made of FASnI 3 -xbai samples that were fabricated under the same experimental conditions for all cells of each type

(a) 0 Current Density /ma cm - 14 1 8 Devices PCE /% FASnI 3 4.0 6 EDAI 0.5% 6.5 4 EDAI 1% 7.4 EDAI % 5.3 EDAI 3% 4. 0 0.0 0.1 0. 0.3 0.4 0.5 0.6 0.7 Voltage /V FASnI 3 0.5% EDAI 1% EDAI % EDAI 3% EDAI (b) IPCE /% 80 70 60 50 40 30 0 0 FASnI 3 FASnI 3-1% EDAI FASnI 3 -% EDAI 4.9 macm -.6 macm - 13.9 macm - 400 500 600 700 800 900 0 00 Wavelength /nm 0 14 1 8 6 Intergated current Density /ma cm - Figure S8. (a) Current-voltage and (b) corresponding IPCE spectra with integrated current densities of the devices made of FASnI 3 -yedai samples 11

Voc /V 0.60 0.55 0.50 0.45 0.40 0.35 0.30 0.5 Jsc /macm - 0 14 1 8 6 FASnI3 1% EDAI % EDAI 3% EDAI FASnI3 1% EDAI % EDAI 3% EDAI 0.8 8 0.7 7 6 FF 0.6 0.5 0.4 PCE /% 5 4 3 0.3 FASnI3 1% EDAI % EDAI 3% EDAI 1 FASnI3 1% EDAI % EDAI 3% EDAI Figure S9. Statistical boxplots of photovoltaic parameters for PSC devices made of FASnI 3 -yedai samples that were fabricated under the same experimental conditions for all cells of each type 1

(a) Voc /V 0.60 0.55 0.50 0.45 0.40 0.35 0.30 0.5 FASnI3 FASnI3-15% BAI FASnI3-1% EDAI (b) Jsc /ma cm - 0 14 1 FASnI3 FASnI3-15% BAI FASnI3-1% EDAI (c) FF 0.8 0.7 0.6 0.5 0.4 0.3 FASnI3 FASnI3-15% BAI FASnI3-1% EDAI Figur e S. Statistical boxplots of (a) Voc, (b) Jsc and (c) FF for reference device FASnI 3 and for devices made with two additives at optimum proportions for 30 devices fabricated under the same experimental conditions for cells of each type 13

(a) 0 (b) 0 Current Density /ma cm - 14 1 8 6 4 Reverse Forward Current Density /ma cm - 14 1 8 6 4 Reverse Forward 0 0.0 0.1 0. 0.3 0.4 0.5 Voltage /V 0 0.0 0.1 0. 0.3 0.4 0.5 0.6 Voltage /V Figure S11. J V characteristics of (a) FASnI 3 -BAI 15 % and (b) FASnI 3 -EDAI 1 % devices with two scan directions: forward scan (from short circuit to open circuit) and reverse scan (from open circuit to short circuit) 14

600 500 FASnI 3 FASnI 3-15% BAI FASnI 3-1% EDAI 1.8 kt/q Voc /mv 400 300 1.3 kt/q 00 1.85 kt/q 0 0 Iight Intensity /W cm - Figure S1. Semi-logarithmic plots of the dependence of light intensity of Voc for FASnI 3, FASnI 3 - BAI 15 % and FASnI 3 -EDAI 1% devices. 15

# (a) FASnI3 (b) FASnI3-15% BAI (c) * FASnI3-1% EDAI * Intensity /a.u. # * * after 6hr after 3hr Intensity /a.u. after 6hr after 3hr Intensity /a.u. * * after 6hr after 3hr (0) fresh fresh fresh 15 0 5 30 35 40 45 15 0 5 30 35 40 45 15 0 5 30 35 40 45 /degree /degree /degree gure S13. X-ray diffraction patterns of films of (a) FASnI 3, (b) FASnI 3 -BAI 15 %, (c) FASnI 3 - EDAI 1 % exposed to ambient conditions (50 % humidity and 0 C) from 0 to 6 h. Symbols * represents the contribution of the ITO substrate and # related to SnI 4. Fi

(a) Current Density /ma cm - 0 14 1 8 6 4 0 Condition J SC /ma cm - V OC /V FF PCE /% Fresh After 7 days After 13 days After 8 days After 41 days. 1.6 0.8 1.0 1.5 0.489 0.483 0.517 0.535 0.564 0.680 0.668 0.678 0.66 0.691 0.1 0. 0.3 0.4 0.5 0.6 Voltage /V 6.0 7.0 7.3 7.4 8.4 fresh 7 days 13 days 8 days 41 days (b) 0 Current Density /ma cm - 14 1 8 6 4 Condition J SC /ma cm - V OC /V FF PCE /% Fresh After days After 4 days After 30 days After 37 days.3 19.6 19.1 19.1 19.9 0.536 0.531 0.59 0.69 0.611 0.694 0.67 0.694 0.686 0.701 0 0.0 0.1 0. 0.3 0.4 0.5 0.6 Voltage/V 6.1 7.0 7.9 8.3 8.5 fresh days 4 days 30 days 37 days Current Density /ma cm - (c) 0 14 1 8 6 4 0 Condition J SC/ /ma cm - Fresh After 7 days After 13 days After 0 days After 38 days 17.9 1. 0.8 1.6 1.7 V OC /V FF PCE /% 0.507 0.477 0.505 0.53 0.557 0.687 0.669 0.689 0.675 0.698 0.1 0. 0.3 0.4 0.5 0.6 Voltage /V 6. 6.8 7. 7.6 8.4 fresh 7 days 13 days 0 days 38 days (d) Current Density /ma cm - 0 14 1 8 6 4 0 Condition J SC /ma cm - V OC /V FF PCE /% Fresh After 7 days After 30 days After 40 days After 60 days 0.1 1.3 1.5 1. 1.1 0.5 0.493 0.57 0.533 0.560 0.7 0.678 0.685 0.703 0.7 7.4 7.1 7.6 7.9 8.4 0.1 0. 0.3 0.4 0.5 0.6 Voltage /V fresh 7 days 30 days 40 days 60 days Figure S14. Current-voltage curves of four FASnI 3 -EDAI 1 % devices at varied durations of storage showing a similar trend of the effect of slow passivation as in Figure 4a of the main text 17

Voc /V 0.65 0.60 0.55 0.50 0.45 0.40 0.35 Fresh 5-days 11-0days 1-30days more than 30 days Jsc /ma cm - 3 1 0 19 17 15 Fresh 5-days 11-0days 1-30days more than 30 days Fresh 5-days 11-0days 1-30days more than 30 days Figure S15. Statistical boxplots showing the variations of Voc, Jsc and FF for 0 encapsulated FASnI 3 -EDAI 1 % devices for varied durations of storage FF 0.78 0.76 0.74 0.7 0.70 0.68 0.66 0.64 0.6 0.60 0.58 0.56

Intensity /a.u. Raw Intensity Peak Sum Background Sn + Sn 4+ Sn + /% Sn 4+ /% 91. 8.8 483 484 485 486 487 488 489 490 491 49 493 Binding energy /ev Figure S. X-ray photoelectron spectra showing the Sn + /Sn 4+ proportions on the surface of a FASnI 3 -EDAI 1 % film after 7 days 19

(a) (b) Figure S17. SEM images of samples of (a) FASnI 3-5%BAI-1%EDAI and (b) FASnI 3-15%BAI- 1%EDAI films. 0

Intensity /a.u. 15% BAI+1% EDAI 5% BAI+%1 EDAI 15% BAI 0 30 40 50 /degree Figure S. XRD pattern of samples of FASnI 3 -xbai-yedai films with varied proportions x and y. 1

Intensity /a.u. FASnI 3 -BAI 5%-EDAI 1%-After 9 Days FASnI 3 -BAI 5%-EDAI 1%-After 5 Days FASnI 3 -BAI 5%-EDAI 1%-Fresh 0 30 40 50 /Degree Normalized PL Intensity 1 0.1 0.01 FASnI 3 -BAI 5%-EDAI 1%- Fresh FASnI 3 -BAI 5%-EDAI 1%- After 5 Days FASnI 3 -BAI 5%-EDAI 1%- After 9 Days 0 0 30 40 50 Time /ns Figure S19. XRD and TCSPC results of fresh and aged (storage periods 5 and 9 days) thin-film sample FASnI 3 -BAI 5%-EDAI 1%.

0 Current Density /ma cm - 14 1 8 6 4 FASnI 3 5% BAI +0.8% EDAI 5% BAI+1% EDAI % BAI+1% EDAI 15% BAI+1% EDAI 5% BAI+% EDAI 15% BAI+% EDAI 0 0.0 0.1 0. 0.3 0.4 0.5 0.6 Voltage /V Figur e S0. Current-voltage curves of devices with FASnI 3 -xbai-yedai perovskites at varied proportions x and y 3

Table S1. Proportion of Sn + and Sn 4+ in various samples at two positions; surface and bulk (after etching 30 s) Samples Sn + /% Sn 4+ /% Sn + /% Sn 4+ /% Without etching (surface) After etching for 30 s (bulk) FASnI 3.3 83.7 73.9 6.1 FASnI 3 -BAI 15 % 76.4 3.6 90.9 9.1 FASnI 3 -EDAI 1 % 88.4 11.6 94.4 5.6 Table S. Time coefficients (relative amplitudes) of the corresponding perovskite films derived from fitting of PL transients (Figure e) Samples τ 1 /ns (A 1 ) τ /ns (A ) τ ave /ns FASnI 3 0. (1.0) FASnI 3 -BAI 15% 0.4 (1.0) FASnI 3 -EDIA 1% 0.6 (0.34) 1.57 (0.66) 1.47 4

Table S3. Photovoltaic parameters of inverted planar heterojunction perovskite solar cells fabricated with varied proportion x in FASnI 3 -xbai under simulated AM-1.5G illumination (power density 0 mw cm ) Devices J SC /ma cm - V OC /V FF PCE /% FASnI 3 best 17.7 0.361 0.67 4.0 average 17.±0.4 0.360±0.01 0.595 ± 0.01 3.7± 0. BAI % best 17. 0.40 0.647 4.7 average 14.3±1.8 0.430±0.01 0.651±0.04 4.0±0.3 BAI 15 % best.0 0.440 0.694 5.5 average 17.±0.7 0.450±0.01 0.67±0.0 5.±0. BAI 0 % best 15.5 0.490 0.705 5.4 average 15.6±0.9 0.45±0.0 0.66±0.0 4.7±0.4 BAI 5 % best 13.8 0.400 0.67 3.5 average 13.6±0.7 0.390±0.01 0.587±0.037 3.1±0.3 5

Table S4. Photovoltaic parameters of inverted planar heterojunction perovskite solar cells fabricated with varied proportion y in FASnI 3 -yedai under simulated AM-1.5G illumination (power density 0 mw cm ) Devices Jsc /ma cm - Voc /V FF PCE /% FASnI 3 best 17.6 0.360 0.67 4.0 average 17.±0.4 0.360±0.01 0.595 ± 0.01 3.7 ± 0. EDAI 1 % best 0.0 0.5 0.7 7.4 average.9±1. 0.511±0.07 0.665±0.039 6.4±0.5 EDAI % best 14.1 0.555 0.670 5.3 average 13.9±1.1 0.538±0.013 0.661±0.045 5.0±0.4 EDAI 3 % best 11.1 0.50 0.719 4. average.5±1.0 0.5±0.01 0.641±0.047 3.5±0.3 6

Table S5. Photovoltaic parameters of inverted planar heterojunction perovskite solar cells fabricated with FASnI 3 under simulated AM-1.5G illumination (power density 0 mw cm ) with active area 0.05 cm Cell no. Voc /V Jsc /ma cm - FF PCE /% 1 0.347.0 0.579 3. 0.348. 0.550 3.1 3 0.36.7 0.583 3.5 4 0.345.9 0.569 3.3 5 0.36 17.4 0.585 3.7 6 0.350 17.4 0.571 3.5 7 0.361 17.7 0.591 3.8 8 0.336 17.8 0.507 3.0 9 0.363 17.6 0.61 4.0 0.361 17.7 0.67 4.0 11 0.354 17.6 0.63 3.9 1 0.353.6 0.586 3.4 13 0.356 17.0 0.615 3.7 14 0.341 17. 0.570 3.3 15 0.404 1.3 0.67 3.1 0.40 1.7 0.617 3. 17 0.401 15.1 0.65 3.8 0.344.6 0.504.9 19 0.330 15.5 0.546.8 0 0.345.1 0.459.6 1 0.336 17.8 0.507 3.0 0.333 15.5 0.53.8 3 0.388 13.0 0.531.7 4 0.94 17.9 0.387.0 5 0.94.0 0.388.1 6 0.354 17.3 0.450.8 7 0.337 17.5 0.438.6 8 0.369 17. 0.463.9 9 0.344 17.8 0.433.7 30 0.350.1 0.46.7 7

Table S6. Photovoltaic parameters of inverted planar heterojunction perovskite solar cells fabricated with FASnI 3 -BAI 15 % under simulated AM-1.5G illumination (power density 0 mw cm ) with active area 0.05 cm Cell No. Voc /V Jsc /ma cm - FF PCE /% 1 0.441 14.5 0.667 4.3 0.439 14.5 0.681 4.3 3 0.45 15.5 0.664 4.4 4 0.48 15.7 0.659 4.4 5 0.41 15.8 0.645 4.3 6 0.47. 0.639 4.4 7 0.4 15.8 0.658 4.4 8 0.440 17.3 0.671 5.1 9 0.439 17.9 0.614 4.8 0.436.1 0.694 5.5 11 0.44.3 0.667 4.8 1 0.453 17.5 0.689 5.5 13 0.441 17.1 0.6 4.6 14 0.441. 0.654 4.7 15 0.419 17.8 0.6 4.7 0.480.0 0.641 4.9 17 0.438 17.7 0.64 5.0 0.438 17.9 0.656 5. 9 0.443 17.3 0.61 4.7 0 0.455.5 0.674 5.1 1 0.449.8 0.58 4.4 0.473 17.1 0.676 5.5 3 0.454 15.9 0.695 5.0 4 0.44 15.6 0.656 4.5 5 0.454.0 0.67 5.0 6 0.453.3 0.658 4.9 7 0.447 17.6 0.668 5.3 8 0.444 17.5 0.648 5.0 9 0.451 17.1 0.684 5.3 30 0.45.8 0.65 5.0 8

Table S7. Photovoltaic parameters of inverted planar heterojunction perovskite solar cells fabricated with FASnI 3 -EDAI 1 % under simulated AM-1.5G illumination (power density 0 mw cm ) with active area 0.05 cm Cell No. Voc /V Jsc /ma cm - FF PCE /% 1 0.538 17.4 0.739 6.9 0.536.3 0.694 6.1 3 0.473.3 0.667 5.8 4 0.5 0.5 0.674 7.1 5 0.514 0.5 0.641 6.7 6 0.545.4 0.709 7.1 7 0.544.4 0.656 6.6 8 0.551.9 0.611 6.4 9 0.543.4 0.586 5.9 0.545 19.1 0.643 6.7 11 0.496 0.6 0.656 6.7 1 0.48 0.7 0.663 6.6 13 0.48 0.4 0.601 5.9 14 0.5 0.1 0.7 7.4 15 0.500.5 0.634 5.9 0.498. 0.649 5.9 17 0.484.5 0.657 5.9 0.489. 0.680 6.0 19 0.5 19.8 0.73 7.3 0 0.507 17.9 0.687 6. 1 0.465 1. 0.608 6.0 0.449 0.5 0.654 6.0 3 0.517 0. 0.65 6.8 4 0.536 17.4 0.715 6.7 5 0.496 17.9 0.609 5.4 6 0.538.0 0.699 6.8 7 0.536.0 0.701 6.8 8 0.487.6 0.64 5.8 9 0.511.0 0.679 6.3 30 0.538.0 0.699 6.8 9

Table S8. Coefficients (relative amplitudes) of the FASnI 3 -EDAI 1% films in tracking the time experiment obtained from fitting the PL transients (Figure 4) Samples τ 1 /ns (A 1 ) τ /ns (A ) τ ave /ns Fresh 0.6 (0.34) 1.57 (0.66) 1.47 After 5 days 1. (0.40).03 (0.60) 1.78 After 15 days 1.45 (0.86) 3.64 (0.14).11 After 0 days.57 (0.65) 5.80 (0.35) 4.34 After 33 days 4.71 (0.83) 15.1 (0.17) 8.88 30

Table S9. Photovoltaic parameters of inverted planar heterojunction perovskite solar cells fabricated with varied proportions x and y in FASnI 3- xbai-yedai under simulated AM-1.5G illumination (power density 0 mw cm ). Devices J SC /ma cm - V OC /V FF PCE /% FASnI 3 17.6 0.360 0.67 4.0 BAI 5 %-EDAI 0.8 %.4 0.480 0.697 6.3 BAI 5 %-EDAI 1 % 19.3 0.530 0.706 7. BAI %-EDAI 1 % 14.4 0.540 0.649 5.1 BAI 15 %-EDAI 1 % 1.4 0.530 0.691 4.5 BAI 5 %-EDAI % 15.1 0.550 0.73 6.0 BAI 15 %-EDAI %.1 0.570 0.687 3.9 31